<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
  </head>
  <body>
    <script>
    // let sum = 0
    // let arr = [1, 2, 3, 4, 5]
    // for (let i = 1; i < arr.length; i++) {
    //   console.log(arr[i])
    // }

    let sum = 0
    let arr = [1, 2, 3, 4, 5]
    for (let i = 0; i < arr.length; i++) {
      console.log(arr[i])
    }
    document.write(`输出数字为：${arr[0]}`)
  </script>
  </body>
</html>